a) Field of the Invention
The present invention relates to the coniguration of an amphibious aircraft which optomizes ergonomic, aerodynamic and hydrodynamic features. These features are designed to provide economic benefits with regard to inital cost, and operation cost without sacrifice in safety.
b) Background of the Invention
In general, the amphibious aircraft is more complex than its land based counterparts due to the dual mission. Water landing requires the aircraft to be engineered to be water tight and withstand the added stress of water impact and docking. The propeller must be protected from the spray. The aircraft must have a safe method for boarding on both land and water. Desirably the aircraft would be designed so as to be able to use a standard boat dock and thus avoid the extra expense of building a special boarding facility. It also is desirable that the aircraft complexity does not degrade aerodynamic performance when compared to comparably sized land based planes.
These design objectives must be met in such a manner that the aircraft is stable on the water, on land and in air. Further, there is the consideration of designing the aircraft so that it is convenient and safe for the pilot and passengers, and yet is integrated so that the various aerodynamic, structural and design features blend together to provide an overall practical, efficient and economical aircraft.
There have been various attempts in the prior art to augment lift by channelling the slipstream created by the propeller. Various portions at the wing or fuselage have been contoured to accomplish this. All of these devices have unfortunately resulted in degradation of cruise performance to the best knowledge at the application.
The present invention comprises an airplane design, and also a method of operating of the airplane. In the preferred form of the present invention, as described herein, the airplane is desirably a seaplane, and more specifically in the test is described as an amphibious airplane. Yet, within the broader scope of the present invention, features of the present invention could be incorporated in an airplane which is not a seaplane.
The airplane of the present invention comprises a fuselage having a longitudinal axis, a vertical axis, a lateral axis perpendicular to the longitudinal and vertical axes, a front end portion, a rear end portion, and a main fuselage portion between the front and rear end portions.
There is a main wing mounted to an upper part of the fuselage main portion, extending generally laterally therefrom as right and left wing sections.
An engine assembly is mounted above the fuselage main body portion and spaced upwardly therefrom. The engine assembly has a propeller means which defines a propeller area through which the propeller rotates. The propeller creates a rearwardly traveling propeller flow stream.
There is a tail means located at a rear portion of the fuselage. This tail means has an aerodynamic surface means to create a vertically aligned aerodynamic force component. The tail means is located rearwardly of the propeller and in the propeller flow stream.
There is a longitudinally extending aerodynamic lift augmenting surface means located over the fuselage main body portion, and this provides an upwardly facing aerodynamic lift augmenting surface longitudinally aligned with the propeller flow stream so that at least a portion of the propeller flow stream flows over the lift augmenting surface means to create augmented lift.
The lift augmenting surface means has a number of unique advantages. First, it is supported by the aircraft xe2x80x9cstrong boxxe2x80x9d which is the main structural support in the fuselage of the airplane. The engine assembly is mounted at this location, as is the lift augmenting surface means. Thus, this alleviates construction costs and potential fatigue problems.
The lift augmenting surface is aligned substantially horizontally to optimize lift, minimize drag and improve airplane performance in cruise operation. Further, since the lift forces created by the lift augmenting surface means are related to the velocity of the propeller air stream, as the thrust of the propeller increases, the ability of the tail means to exert a downward aerodynamic force to maintain the stability of the airplane is enhanced.
In the preferred configuration, the lift augmenting surface means has in transverse cross section a concavely curved surface portion, and the propeller is located adjacent to this concavely curved surface portion, with the path of the propeller and the curvature of the surface portion being concentric and these also placed closed adjacent to one another.
In the preferred form, the lift augmenting surface means has a center of lift positioned forwardly at the propeller means. Also, desirably the concavely curved surface portion has an arcuate length between about a right angle and one half of a right angle, with a presently preferred configuration having the arcuate length of about 70xc2x0. Also, desirably, the lift augmenting surface means is substantially horizontally aligned. For design balance, there may be a slight downward and rearward slope, but this should be no greater than a fourteen to one slope, since a greater slope would unnecessarily create an aerodynamic force component that would increase drag. Also, in the preferred form, the engine assembly comprises a push engine which is mounted above the lift augmenting surface means, and also desirably mounted by a strut from the main central structural box of the airplane.
In the preferred form, the airplane is adapted to takeoff from, and land on, a water surface. The fuselage has a passenger section with an access location by which a pilot and/or passengers can move into and out of the passenger section. The airplane comprises substantially horizontally aligned platform means extending laterally from the fuselage adjacent to the access location. More specifically, there are right and left platforms on opposite sides of the fuselage, and each platform comprises a main platform portion and a strake having a highly swept leading edge extending from its related main platform portion forwardly along the fuselage.
In the preferred form, each of the platforms has a forward platform portion and a rear platform portion. The forward platform portion is positioned forwardly of a leading edge of the main wing, and the rear platform portion is positioned longitudinally behind the leading edge of the main wing. At least the rear main platform portion is aerodynamically aligned so as to alleviate possible aerodynamic interference with air stream flow around the main wing.
The strakes are both arranged to generate at higher angles of attack a vortex which travels over the main platform portion to create vortex generated lift. The main wing is characterized in that at a predetermined angle of attack of the airplane, the main wing reaches an initial stalling condition. Each strake is aerodynamically arranged to continue generating a strong vortex flow over its main platform portion at the predetermined angle of attack to generate vortex induced lift to alleviate an initial stall condition of the main wing.
The airplane has an airplane reference mean aerodynamic chord (MAC) and also a quarter chord (mean aerodynamic chord) point. Components of the airplane are, for purposes of definition, considered as having a percentage distance forwardly or rearwardly of the airplane reference quarter chord MAC point, with distance being measured as a percentage value where one hundred percent is the length of the airplane reference mean aerodynamic chord.
Various components of the airplane are located within ranges in accordance with this reference point and reference distance.
The center of gravity of the airplane should be no greater than fifty percent forward of the quarter chord MAC point and no greater than greater than twenty five percent rearwardly of the chord MAC point. Also, this center of gravity should be forward of the center of lift of the airplane. Desirably it should be at least thirty three percent forward of the quarter chord MAC point.
The augmenting lift surface has a center of lift, and this is optimally located at about seventy five percent rearwardly of the quarter chord MAC point, and within a broader range is between zero to one hundred and twenty five percent rearwardly of the chord to chord MAC points.
In the passenger section, there is passenger seat means which is positioned desirably at a location at the center of gravity of the airplane. Within broader limits this passenger seat means should be positioned within fifty percent of the center of gravity of the airplane. Thus, passengers being seated at the passenger seat means does not significantly affect the location of the center of gravity.
With regard to the location of the two strakes, the forward end of each strake should be between about one hundred percent to two hundred fifty percent forward of the reference chord MAC point. The leading edge of the main platform is desirably located about fifty percent to one hundred fifty percent forward of the reference quarter MAC point.
There are other relationships of the aerodynamic features, force components and moments which are significant in the present invention. These and other features of the present invention will become apparent from the following detailed description.